The invention relates to telecommunications networks, and more particularly to selecting restoration paths in a telecommunications network.
Modern telecommunication networks are reconfigurable and provide for fast restoration from network failures. For example, and in the context of optical networking, Synchronous Optical Network (SONET) rings provide the primary technology for optical layer communication and restoration from network failures. SONET rings tend to be capacity inefficient when compared to “mesh” topologies in networks with a high degree of connectivity and when, because of size limitations, connections are forced to route through many interconnected rings. As optical-cross connects (OXCs) are deployed within today's transport networks based on wavelength-division multiplexing (WDM), the potential emerges to provide on-demand establishment of high-bandwidth connections (also referred to in the art as “lightpaths”). Emerging standards such as Multi-Protocol Lambda Switching (“MPL(ambda)S”) provide a standardized optical network control plane that is essential for building an effective platform for vendor interoperability. See, e.g., D. Awduche et al., “Multi-Protocol Lambda Switching: Combining MPLS Traffic Engineering Control with Optical Crossconnects,” IETF Internet Draft, http://www.ietf.org/internet-drafts/draft-awduche-mpls-te-optical-01.txt (November 1999). Unfortunately, few recent contributions to the art have addressed the need for fast failure restoration in such networks.
In co-pending commonly-assigned United States Utility patent application, “METHODS AND SYSTEMS FOR FAST RESTORATION IN A MESH NETWORK OF OPTICAL CROSS CONNECTS,” Ser. No. 09/474,031, filed on Dec. 28, 1999, which is incorporated by reference herein, a restoration methodology is disclosed that utilizes pre-computed restoration routes disjoint from the normal communication path—but wherein the channels/wavelengths may be chosen dynamically during the restoration process. The invention therein disclosed can potentially provide restoration competitive with SONET ring restoration speeds. There is, however, still a need for a flexible and practical methodology for selecting an advantageous restoration path that may be utilized in a restoration process such as the one disclosed in the above application. Moreover, there is a need for a distributed approach to restoration that permits the information needed for restoration path selection to be distributed throughout the network with a minimum amount of signaling overhead.